Image intensifier densitometer

ABSTRACT

An image intensifier densitometer is provided with a collimator which is composed of laminations. The length-to-distance relationship of the laminations determines the shape and the proportions of the measuring area of the image intensifier densitometer in conjunction with the focal distance of the basic objective of the image intensifier and the electron-optical enlargement of the image intensifier.

United States Patent Buchmann 1 1 Oct. 1, 1974 15 IMAGE INTENSIFIER DENSITOMETER 3,271,740 9/1966 Alabinow 250/213 VT I t F B h H b 3,417,242 12/1968 Windebank 250/213 VT 1 man, am 3,665,191 5/1972 Moody 250/213 VT e man FOREIGN PATENTS OR APPLICATIONS [73] Asslgnee' gb g Cwporamm New 1,462,229 7/1965 France 250/237 [22] Filed: Jan. 24, 1973 Primary ExaminerJames W. Lawrence Assistant Examiner-C. E. Church [21] Appl' 326255 Attorney, Agent, or FirmFrank R. Trifari [30] Foreign Application Priority Data [5 7] ABSTRACT Feb. 15, 1972 Germany 2207053 An image intensifier densitometer is provided with a collimator which is composed of laminations. The [52] US. Cl 250/213 VT, 250/505 length-to-distance relationship of the laminations de- [51] Int. Cl. G03b 41/16 termines the shape and the proportions of the measur- [58] Field of Search 250/213 VT, 505 ing area of the image intensifier densitometer in conjunction with the focal distance of the basic objective [56] References Cited of the image intensifier and the electron-optical en- UNITED STATES PATENTS largement of the image intensifier.

Dunn 250/213 VT 11 Claims, 9 Drawing Figures 1 IMAGE INTENSIFIER DENSITOMETER The invention relates to an image intensifier densitometer, comprising an X-ray source and an X-ray image intensifier having a basic objective and one or more measuring devices.

In X-ray densitometry or in apparatus for the timedependent measurement and recording of the attenuation of X-rays upon irradiation of a (human) body by means of an image intensifier, also referred to as densitometry for the sake of simplicity, the intensity of the X-radiation attenuated by the object is measured, via a specially shaped, for example, slit-like or circular scanning surface, during a given period of time and is recorded by means of a recorder or is directly applied to another processing system, for example, to an electronic data processing system. Densitometry utilizing a slit-like measuring surface is known as kymography. The latter technique enables in particular the display of the movement function of an organ or part of an organ, for example, the heart wall, which periodically moves over the measuring surface.

X-ray densitometry requires a measuring surface which is adapted to the relevant measuring problems, and suitably proportioned electronic apparatus. The X-ray source itself must be sufficiently stable as otherwise a relative measurement is required so as to take into account the fluctuations in the radiation intensity of the X-ray source.

It is known that this object can be achieved by means of, for example, the so-termed video densitometry as appears from Rofo 108, 79 88 (1968) Videodensitometrie, technische Grundlagen und klinische Anwendung als Ferneshkymographie by J. Lissner and P. Marhoff, and from Elektromedizin 12, 82 95 and 145 157 (1967) Rfintgenologische Kontrastmitteldichtemessungen zur Untersuchung der Herzund Kreislauffunktion by P. Heintzen, J. Biirsch, P. Osypka and K. Moldenhauer. in video densitometry an image of an X-ray image intensifier which is present as a television signal is analyzed by means of a measuring window; the measuring window is generated by an additional window generator. Eventhough the video densitometry offers the advantage that imageswhichare recorded on magnetic tape can also be densitometrically examined, the use of this method has the drawback that the linearity is substantially limited and that only limited brightness differences can be evaluated.

From Rontgenblatter 23, 593 598 (1970) Ergebnisse der Rontgen-Kino-Densitometrie by F. Heuck, H.K. Deininger and K. Vanselow and Kreislaufanalyse mittels Rontgendensitometrie by W. Rutishauser, Bern-Stuttgart-Wien (1966) it is furthermore known to perform X-ray densitometry on a film..This film densitometry is very suitable for the examination of contrast medium-passage through blood vessels after aniography. However, this method has the drawback that the non-linearity of the film causes problems, that the result is not immediately available, and that the examination cannot be readily repeated on the object itself.

Also known is the kymography as described by H. Vieten: Handbuch der medizinischen radiologie, volume 111, pages 407 435, Berlin-Heidelberg-New York (1967), Elektrokymographie" by K. Heckmann and R. l-laurich, in which a similar but slightly more restricted object is pursued. Because the surface kymography must be considered only as a variant of the invention relating to electrokymography, a brief description of the latter will suffice. According to this known method the fluctuations in the brightness which occur in a luminescent screen or a similar scintilator are mea sured via a slit by means of a photoelectric receiver, immediately after irradiation of the object, the said fluctuations being recorded as a function. Movements of the organs are thus displayed. The direct electrokymography, however, has the drawback that the measuring member must be adjusted by means of a fluoroscope and that such a simultaneous fluoroscopic check is substantially hampered.

The described drawbacks are eliminated by an apparatus according to the invention. Because an electronoptical image intensifier linearly transfers brightnesses over a comparatively large region, the use of an imageintensifier image for X-ray densitometry makes sense. It might be possible to use a real optical image of a given image area corresponding to the desired measuring surface. However, this method is unattractive because of the comparatively high cost of the objective and the time-consuming adjustment since the image intensifier image is reduced at a l l0 ratio with respect to the X-ray-image.

Assuming that for a normal application of an image intensifier for x-ray fluoroscopy a so-termed basic objective is already present which is combined with a camera objective to form a so-termed tandem objective, the use of an optical element, arranged between the two objectives, is very advantageous for the desired measuring technique. Use is then made of the circumstance that the basic objective distributes the information which is situated in its focal plane and which differs in accordance with its location in the image, in various directions. Behind the basic objective each image point corresponds to a light beam, the lateral dimension of which is determined by the objective limitation, the rays of the said beam being parallel with respect to each other, the direction of the said beam corresponding to the direction of the connecting line between the relevant object point and the intersection of the optical axis and the entrance pupil of the objective.

In agreement with this insight, an image intensifier densitometer of the kind set forth according to the invention is characterized in that a receiver of the measuring device is constructed as a mechanical collimator which comprises laminations, the length-to-distance relation of the laminations determining, in conjunction with the focal distance of the basic objective of the image intensifier and the electron-optical enlargement of the image intensifier, the measuring surface of the image intensifier densitometer.

Two collimators which are formed by laminations can then be arranged one behind the other and rotatable with respect to each other such that this rotation produces different measuring fields. Alternatively, two or more collimators producing different measuring fields can be arranged adjacent to each other to enable a quick selection of one of these measuring fields. In a further preferred embodiment one common photocell, for example, a secondary-emissive electron multiplier, is used for a plurality of collimators, the selection of the measuring field being performed by a mechanical device. Two collimators can also determine different measuring fields, notably measuring fields of different proportions, and two photocells or one mechanical device for one photocell can perform a relative measurement via the two measuring fields. Furthermore, the intensity of the X-rays or the sensitivity of an electric amplifying system of the measuring device can be controlled via one of the measuring fields.

In a further preferred embodiment yet according to the invention a light source can be arranged adjacent to the photocell such that the exact position and shape of the measuring field corresponding to the relevant collimator can be displayed on the secondary screen of the image intensifier. The measuring device incorporating one collimator or a plurality of collimators can be used on an output side of an image divider of known construction. The control of the X-rays or of the sensitivity of the measuring system can be effected, however, with a larger time constant in the measuring field in which measuring takes place. The collimator can also be arranged to be vertically rotatable with respect to the beam path. The measuring field is shifted as a result of this rotation.

Some embodiments according to the invention will be described in detail with reference to the drawings.

FIG. 1 shows a basic diagram of an image intensifier densitometer device according to the invention,

FIG. 2 shows a detail of FIG. 1 at an enlarged scale so as to illustrate the operation of a collimator,

FIG. 3 shows an embodiment incorporating two collimators having a different operating principle,

FIG. 3a compares the measuring fields of the two collimators of FIG. 3,

FIG. 4 is a diagrammatic representation of a device according to the invention incorporating collimators which serve different purposes,

FIG. 5 shows a preferred embodiment incorporating two consecutively arranged collimators,

FIG. 5a shows the measuring field of the consecutively arranged collimators of FIG. 5 at various rotary positions thereof,

FIG. 6 shows a preferred embodiment incorporating a plurality of collimators which are to be selected, and

FIG. 7 shows a collimator with an associated light source.

FIG. 1 shows an optical axis 1 of a device comprising an X-ray source 2, an X-ray image intensifier 3 having a primary screen 4 which faces the X-ray source 2 and which is arranged on the X-ray image intensifier 3. A secondary luminescent screen 5 is arranged on the output side of the image intensifier. In the X-ray image intensifier 3, the image is reduced at a ratio of approximately 1 l0 in this embodiment, going from the primary screen 4 to the secondary screen 5. The device furthermore comprises a basic objective 6 with a photocell 7 and an electronic device or a recorder 8. The device described thus far is generally known. In accordance with the invention a collimator 9 is arranged be tween the basic objective 6 and the photocell 7. Embodiments of this collimator will be described hereinafter with reference to the Figures.

A collimator 9 can be composed of, for example, a cubical or cylindrical housing in which laminations are provided which preferably extend in parallel and which are blackened and made of a thin metal. The shape, the dimensions and the distance with respect to each other or the opening of the laminations co-determine the shape and dimensions of the measuring surface.

FIG. 2 again shows the optical axis 1 and the basic objective 6. The collimator 9 has a depth b, a height 0 or a diameter 0 in the case of a cylindrical execution, and a shaft opening a. This shaft opening corresponds to the distance between two laminations or shaft walls 10 in the device under consideration.

The basic objective 6 has a focal distance f. In the plane of the luminescent screen 5 the letter x in FIG. 2 denotes the dimensions of the measuring field, for example, one slit width in the direction under consideration. The value of x follows from the formula a/b 2 f =x, so x is a function of the focal distance f of the basic objective 6 and of the geometrical dimensions of the collimator. The quotient a/b produces the said lengthto-distance relationship or the shaft relationship of the collimator.

The basic objective 6 and two different collimators l1 and 12 are arranged about the optical axis 1 in FIG. 3. In the collimator 11, the shaft walls 10 are comparatively far from each other, so that a measuring field dimension 2: as shown in FIG. 3a is produced. In contrast therewith the collimator 12 has shaft walls 10 which are situated comparatively close together, so that a measuring field dimensions x is produced which is also shown in FIG. 3a. The measuring field dimension x is concentric with respect to the measuring field dimension x because both collimators l1 and 12 are arranged parallel to the optical axis 1. The measuring fields are shown in a plane at a mutually equal distance from the basic objective 6 in this Figure, but this is not necessary.

FIG. 4 shows the X-ray source 2, the image intensifier 3, the basic objective 6 and the collimators l3, l4 and 15 which are arranged in accordance with the invention. A photocell 7 is arranged on the output side of each of the collimators. A measuring device 16 is connected to the outputs of the two photocells 7 which are arranged behind the collimators l3 and 14. One input of a control amplifier 17 is connected to the output of the photocell 7 which is arranged behind the collimator 15, whilst an output 18 of the control amplifier 17 is connected to the measuring device 16, a further output 19 of the control amplifier 17 being connected to an X-ray generator 20. The X-ray. generator 20 is connected to the X-ray source.

When the control amplifier 17 is switched on, either the sensitivity of the measuring device 16 or the X-ray dose of the X-ray source 2 can be controlled in accordance with the brightness of the measuring field selected by the collimator 15.

The reference 1 in FIG. 5 again denotes the optical axis, and the reference 6 the basic objective. Two laminated collimators 21 and 22 are constructed in the same manner and are consecutively arranged parallel to the optical axis 1 and rotatable with respect to each other about an axis 23. The measuring fields thus produced are shown in FIG. 5a. In the case of parallel laminations and consecutively arranged collimators 21 and 22, a horizontal slit 24 or a vertical slit 25 of the measuring field arises, and upon rotation of the collimators 21 and 22 through with respect to each other, the collimators being the same, a square measuring field 26 arises, the side 27 of which is equal to twice the width 28 of the slits 24 and 25.

FIG. 6 shows a'preferred embodiment enabling adjacently arranged collimators 29, 30 and 31 to be successively selected in time. The reference 6 again denotes the basic objective and the reference 7 the photocell. The collimators 29, 30 and 31 have different shaft ratios. A mechanical diaphragm 32 permits of individual selection of the collimators 29, 30 and 31. To this end, only the position of the aperture 33 of the diaphragm 32 must be adjusted in known manner to the output of the selected collimator.

The reference 1 in FIG. 7 again denotes the optical axis, and the reference 6 the basic objective. A collimator 34 is arranged parallel to the optical axis 1. Adjacent to the photocell 7 a light source 35 is arranged on the output side of the collimator 34. The photocell 7 is properly shielded from the light source. When the light source 34 is switched on, a bright area appears on the secondary screen 5 of the image intensifier, the said area corresponding to the measuring field. This measuring field indication can always be used between measurements so as to check the measuring field position. When the brightness of the light source 35 is known, this source can be used not only for indicating the measuring field, but also for calibrating the image intensifier densitometer. For this purpose it is sufficient that the stabilized light source 35 of known brightness and the photoelectric receiver 7 are simultaneously used.

What is claimed is:

1. An X-ray densitometer, comprising:

an X-ray source for irradiating at least a portion of an object to produce an X-ray densitometric image;

an X-ray image intensifier having a primary screen for receiving said X-ray densitometric image and having a secondary screen for converting said X-ray image into an optical image;

a convex lens positioned with the focal plane thereof coincident with said optical image;

a mechanical collimator positioned on the side of said convex lens remote from said optical image to receive light passing through said lens from said optical image, said collimator not passing light which travels thereto from directions outside of a range of directions determined by the optical characteristics of said collimator, said range of directions corresponding with light coming from only a portion of said optical image;

a light sensitive device positioned adjacent said collimator to receive and measure light passed by said collimator from said portion of said optical image, said portion of said optical image being the measuring field.

2. An X-ray densitometer as defined in claim 1 wherein said collimator is of laminar construction.

3. An image intensifier densitometer as claimed in claim 2, characterized in that for a quick selection of a measuring field a plurality of collimators having mutually different measuring fields with respect to the image plane are adjacently arranged.

4. An image intensifier densitometer as claimed in claim 3, characterized in that for a plurality of collimators one common light sensitive device is used, the selection of the measuring field being performed by mechanical alignment thereof.

5. An image intensifier densitometer as claimed in claim 2, characterized in that two collimators determine different measuring fields a light sensitive device being provided for each collimator for relative measurements between the two measuring fields.

6. An image intensifier densitometer as claimed in claim 5, characterized in that via one of the measuring fields the intensity of the X-rays or the sensitivity of an electronic intensifying system incorporated in the measuring device can be controlled.

7. An image intensifier densitometer as claimed in claim 2, characterized in that adjacent to the light sensitive device a light source is arranged by means of which light energy may be directed back through the collimator to determine the exact position and shape of the measuring field corresponding to the collimator on the secondary screen of the image intensifier.

8. An image intensifier densitometer as claimed in claim 2, characterized in that a known image divider is arranged between the secondary display screen of the image intensifier and the collimator device.

9. An image intensifier densitometer as claimed in claim 2, characterized in that the measuring field controls either the X-ray intensity or the sensitivity of the measuring system.

10. An image intensifier densitometer as claimed in claim 2, characterized in that the collimator may be moved tangential to the light propagation direction in order to shift the measuring field.

11. An image intensifier densitometer as claimed in claim 2, characterized in that two laminated collimators are arranged one behind the other such that they are rotatable with respect to each other for the selec' tion of different measuring fields.

UNITED STATES PATENT OFFICE I 15/ 9) e v CERTIFICATE OF CORRECTION Patent No. 9' 3 Da-ted ctoberl. 1974 Inven t or(s) FR AN Z BUCHMANN It is certified that error appears in the above-identified patent v andthat said Letters Patept are hereby corrected as shown below:

IN THE TITLE PAGE In section [30] P2207053" should bee- 22070533 sighed and sealed this 3rd day of December 1974.

(SEAL) t Attest: I I McC OY M. GIBSON JR. c. MARSHALL DANN Attesting Officer Commissioner of Patents 

1. An X-ray densitometer, comprising: an X-ray source for irradiating at least a portion of an object to produce an X-ray densitometric image; an X-ray image intensifier having a primary screen for receiving said X-ray densitometric image and having a secondary screen for converting said X-ray image into an optical image; a convex lens positioned with the focal plane thereof coincident with said optical image; a mechanical collimator positioned on the side of said convex lens remote from said optical image to receive light passing through said lens from said optical image, said collimator not passing light which travels thereto from directions outside of a range of directions determined by the optical characteristics of said collimator, said range of directions corresponding with light coming from only a portion of said optical image; a light sensitive device positioned adjacent said collimator to receive and measure light passed by said collimator from said portion of said optical image, said portion of said optical image being the measuring field.
 2. An X-ray densitometer as defined in claim 1 wherein said collimator is of laminar construction.
 3. An image intensifier densitometer as claimed in claim 2, characterized in that for a quick selection of a measuring field a plurality of collimators having mutually different measuring fields with respect to the image plane are adjacently arranged.
 4. An image intensifier densitometer as claimed in claim 3, characterized in that for a plurality of collimators one common light sensitive device is used, the selection of the measuring field being performed by mechanical alignment thereof.
 5. An image intensifier densitometer as claimed in claim 2, characterized in that two collimators determine different measuring fields a light sensitive device being provided for each collimator for relative measurements between the two measuring fields.
 6. An image intensifier densitometer as claimed in claim 5, characterized in that via one of the measuring fields the intensity of the X-rays or the sensitivity of an electronic intensifying system incorporated in the measuring device can be controlled.
 7. An image intensifier densitometer as claimed in claim 2, characterized in that adjacent to the light sensitive device a light source is arranged by means of which light energy may be directed back through the collimator to determine the exact position and shape of the measuring field corresponding to the collimator on the secondary screen of the image intensifier.
 8. An image intensifier densitometer as claimed in claim 2, characterized in that a known image divider is arranged between the secondary display screen of the image intensifier and the collimator device.
 9. An image intensifier densitometer as claimed in claim 2, characterized in that the measuring field controls either the X-ray intensity or the sensitivity of the measuring system.
 10. An image intensifier densitometer as claimed in claim 2, characterized in that the collimator may be moved tangential to the light propagation direction in order to shift the measuring field.
 11. An image intensifier densitometer as claimed in claim 2, characterized in that two laminated collimators are arranged one behind the other such that they are rotatable with respect to each other for the selection of different measuring fields. 